Why to use DB2 DCLGEN instead of COPY?

[Kamini Gupta]

Hi,

Why to we use DB2 DCLGEN instead of COPY? Can not that make just same impact?

[Robert Sample]

SQL statements are run through a preprocessor before the COBOL compile is done. The COPY statement is a COBOL verb and hence will not be invoked until the compile, which is after the preprocessor has completed. So using a COPY instead of DCLGEN means nothing will be available to SQL since the preprocessor will not have anything to work with.

[Kamini Gupta]

Thanks Robert. But if use COPY COPYBOOK with DCLGEN variables, when they will be used by program, program will get them and it will work, right?

[Robert Sample]

The IBM manual at https://www.ibm.com/support/knowledgece ... clgen.html says

The declarations generator (DCLGEN) produces an SQL DECLARE TABLE statement and a COBOL, PL/I, or C data declaration for a table or a view named in the catalog.

So the DCLGEN does the SQL DECLARE TABLE for which the fields can then be referenced in a copy book.